What is Nitrogen Depositon?
In terrestrial ecosystems such as forests and grasslands, nitrogen (N) is an important but scarce nutrient. Nitrogen is plentiful in the atmosphere, but nearly all of this N exists in a stable, unreactive chemical form (N2) that is inaccessible to most organisms. Natural processes such as lightning transform some of this unreactive N to reactive forms such as ammonium (NH4+) and nitrate (NO3-). After this reactive N is formed, it is often moved into downwind terrestrial ecosystems in rain or dust, a process called atmospheric depostion.
Human Activities Have Changed Nitrogen Deposition
In addition to the natural sources of reactive N, human activities such as agriculture, transportation, and industry are also capable of creating reactive N and adding it to the atmosphere. Since the industrial revolution, the amount of reactive nitrogen (N) deposited from the atmosphere onto terrestrial ecosystems has increased by an order of magnitude across large areas of the Northern Hemisphere (from 50-100 milligrams of N per meter 1500-2000 milligrams of N per m2 per yr). These large additions of reactive N have the potential to alter many of the fundamental ways in which ecosystems function—ranging from affecting the growth and vigor of trees to changing the quality of water flowing into our streams and aquifers.
The Michigan Nitrogen Deposition Gradient study was established in 1987 in order to examine the effects of climate and atmospheric deposition on ecosystem processes in the Great Lakes region and continues today with support from the National Science Foundation and the Department of Energy.The primary purpose of this study is to research the mechanisms controlling carbon and N cycling in the face of chronic atmospheric N deposition. These investigations have spanned a broad array of topics, ranging from the genes and enzymes important in the mircobial breakdown of plant organic matter in the soil to the growth and death of trees that are more than 100 years old. Details of this research can be found on our publications page.
In addition to research, this project has an important educational mission. Dozens of undergraduate and graduate students have gained valuable research training from the project. Also, the field sites and research results are used as important resources to train K-12 science teachers as part of the Global Change Teachers Institute, conducted each summer at Michigan Technological University.